US 4,127,946 A · Method for steam drying

Abstract

A method and apparatus are disclosed for drying materials by contact with a drying gas consisting essentially of internally generated superheated drying steam above 212.degree. F., to vaporize the water in the material and remove it to produce the steam used for drying. A minor portion of steam is removed from the drying gas and discarded to maintain pressure equilibrium. The drying steam is produced within the drying chamber from water evaporated from the material being dried and is either heated within the drying zone where it is in contact with the material or removed from the drying zone, heated to form superheated steam, and returned to the drying zone for contact with the material during drying. A wood veneer dryer employing the invention is described as well as an apparatus for drying particulate material. The drying zones provided with the veneer dryer have at least along the major portions of their lengths a negative internal pressure which is below that of the ambient external atmosphere outside the dryer to prevent pollutants from leaking out of the dryer and ambient air is prevented from entering the dryer into such drying zone.

Claims10

Dependent claims

A drying method for removing water from a water containing material to provide a dried product which comprises the steps of:

contacting said water containing material, in a drying zone at drying conditions, with a recycled drying fluid comprising at least a major portion of superheated steam at a first temperature above the boiling temperature of water, whereby at least a portion of the water in said material is vaporized, removed from said material, and comingled with said drying fluid to form an effluent gas stream comprising steam at a second temperature lower than said first temperature;
removing said effluent gas stream from said drying zone and heating said effluent gas stream to about said first temperature;
discarding a minor first portion of said heated effluent gas stream and recycling a major second portion of said heated effluent gas stream to said drying zone to provide said recycled drying fluid;
producing a negative pressure in said drying zone along at least a major portion of its length, said negative pressure being below the ambient pressure of the atmosphere surrounding said drying zone;
and
transporting said material through said drying zone along its length from an inlet to an outlet during drying and removing said material from said outlet to provide said dried product.

3 more elements

Dependencies are inferred from the claim text.

Method for steam drying

Life of this patent

Method for steam drying

Life of this patent

Abstract

Claims10